1. Field of the Invention
The present invention relates to a speed reducer, and more particularly to a planet gear speed reducer.
2. Description of Related Art
In the mechanism field, a speed reducer is usually used to provide low RPM and high torsion for operating a high load apparatus. The conventional speed reducers are divided into two types, such as gear box speed reducers and planet gear speed reducers. The gear box speed reducer does not concern about the scope of the present invention. Hereinafter, only the planet gear speed reducer is described.
A conventional planet gear speed reducer uses two bearing to support an output shaft in a casing of the speed reducer. A bearing is mounted in a gear arm of the output shaft for supporting the input shaft. A sun gear axle extends from the input shaft for driving a planet gear set that is disposed on the gear arm of the output shaft to output power via the output shaft.
The conventional planet gear speed reducer only provides a bearing between the output shaft and the input shaft for concentrically connecting the output shaft and the input shaft, and the planet gar set is driven by a free end of the sun gear axle. Consequently, the concentricity between the input shaft and the output shaft may be reduced because the error during assembling the two shafts and the not precise manufacturing of the input shaft. In addition, operating sun gear axle will enlarge the error between the output shaft and the input shaft such that the sun gear axle the planet gear set is easily worn out and the use life is shortened.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional planet gear speed reducer.